A manhunt is underway as police search for a person who exposed himself to a woman alone on a beach before approaching her. The 25-year-old woman walked through Alva Beach Park before sitting on the beach in Ayr, south of Townsville, about 9.15am on Thursday. Police said that a short time later, an unknown man entered the beach from a walking track to the south of where the woman arrived. The man then started to approach the woman, and she run away via the southern walking track. Police released a computer-generated image of a man who they said may be able to assist with the investigation.